Photodetector circuits are utilized in various devices (e.g., focal plane arrays and other photo-sensing circuits) to sense incident light in the visible and non-visible spectra. Certain photodetector circuits employ one or more position sensitive detectors (PSDs) that can measure a position of incident light upon the PSD.
Traditionally, individual PSDs are constructed from a PiN diode or similar device. FIG. 1 depicts a typical PSD 10. PSD 10 may include a semiconductor substrate 12 which includes a PN junction. Illumination 18 may impinge substrate 12 at a location 20, generating a photocurrent by means of the photovoltaic effect. Such photocurrent may flow through one or more of anodes 14 and cathode 16 depending upon the location of the incident illumination 18. Accordingly, the position of location 20 may be computed by analyzing the currents ix1, ix2, iy1, and iy2 (e.g., location coordinates x and y may be computed by the equations x=Kx(ix2−ix1)/(ix2+ix1) and y=Ky(iy2−iy1)/(iy2+iy1), where Kx and Ky are scaling constants based on size, electrical characteristics, and other properties of PSD 10).
However, traditional PSDs have many disadvantages. For example, conventional PSDs do not permit detection of infrared wavelengths. In additional, traditional approaches to fabricating PSDs do not readily permit optimizing electrical parameters of the PSDs, such as substrate/sheet resistance and contact resistance.